1. Field of the Invention
The present invention is generally related to snorkels used by skin divers and swimmers. More particularly, this invention is concerned with preventing water from entering and flooding a snorkel.
2. Description of the Prior Art
Skin divers and swimmers use the snorkel as a means to breathe while swimming face down on the water surface. The snorkel functions as a conduit between the diver's mouth and the overhead air. Typically, the open end of the snorkel conduit extends a short distance above the water surface. Occasionally, due to swimming movements or wave action, small amounts of water flow or splash into the open end of the snorkel and partially floods the conduit. An experienced skin diver can sense when water enters the snorkel and responds by immediately stopping inhalation. Respiration is resumed after the snorkel has been purged of water. Inexperienced skin divers find occasional flooding especially troublesome because, undetected, water can be inhaled resulting in coughing and extreme discomfort.
Water will also flood the snorkel when the swimmer deliberately dives below the water surface. The snorkel conduit will be completely flooded with water when the swimmer returns to the surface. When the open end of the snorkel is again above the water surface, the flooded conduit is purged for respiration by exhaling an explosive blast of air into the mouthpiece.
Surface tension forms the purging blast of air into a bubble that spans the cross section of the snorkel conduit. Pressure within the bubble expands the bubble toward the open end of the conduit. As the leading surface of the bubble moves away from the mouthpiece, the bulk of the water within the conduit is pushed ahead of the bubble and out the open end.
The purging bubble of air will slip past water that adheres to the inside surface of the conduit. After the purging air bubble is spent, residual water will flow down the inside surface toward the mouthpiece. Also, water which splashes into the open end of the snorkel conduit due to swimming movements or wave action will typically strike and adhere to the inside surface of the conduit and thereafter flow toward the mouthpiece. Water accumulates at the lowermost portion of the snorkel conduit, typically adjacent the mouthpiece, and can soon obstruct the conduit. Unless the conduit is completely blocked, a slow and cautious inhalation is possible after which another purging exhalation can be made.
The respiratory effort needed to purge a snorkel is significant. Many skin divers and swimmers lack the respiratory strength needed to completely purge a flooded snorkel with a single exhalation, and must repeat the purging procedure several times. Also, water will sometimes enter the snorkel just as the swimmer has completed an exhalation, leaving very little air in the lungs to satisfactorily complete a purge.
As a consequence of the difficulties typically encountered by a skin diver or swimmer when trying to purge a flooded snorkel, a number of inventions have been proposed to protect the snorkel opening with devices that prevent water from entering the conduit, even when the swimmer dives underwater.
U.S. Pat. No. 2,317,236 titled Breathing Apparatus for Swimmers, issued to C. H. Wileri, et al, on Apr. 20, 1943, teaches an inverted opening with a caged buoyant ball arranged to block the above water end of the snorkel whenever water starts to enter. Such inverted ball valves are bulky, tend to snag, often fail to seal completely and, also, significantly increase respiratory effort. Although once popular, such devices are now considered unreliable and obsolete.
U.S. Pat. No. 4,071,024 titled Snorkel, issued to Max A. Blanc on Jan. 31, 1978, teaches an air-entrapping cap which is mounted on the above water opening of the snorkel. A tortuous passage in the cap retards water flow into the snorkel. Although such a cap is somewhat effective in blocking the occasional splash of surface water into the snorkel, it also retards expulsion of water that enters the snorkel during a dive below the water surface. The significant increase in respiratory and purging effort limits its utility and subsequent popularity.
U.S. Pat. No. 4,805,610 titled Swimmer's Snorkel, issued to Howard Hunt on Feb. 21, 1909, teaches a buoyant cap attached to an internal non-buoyant ball valve which is arranged to block the snorkel opening whenever water covers the cap. As with the valve of Wilen, the Hunt valve is bulky, tends to snag, and does not reliably prevent water from entering the snorkel.
U.S. Pat. No. 5,117,817 titled Vertical Co-Axial Multi-Tubular Diving Snorkel, issued to Hsin-Nan Lin on Jun. 2, 1992 teacher an annular float arrangement which blocks the above water end of the snorkel whenever water starts to enter. To assist in purging, the Lin snorkel also teaches a secondary purge tube within the breathing conduit. The Hoin-Nan Lin snorkel is an improvement over Wiler. However, the valve arrangement of the Hsin-Nan Lin snorkel significantly increases respiratory effort, and if water somehow gets into the snorkel, for example through the mouthpiece, that water is difficult to expel.
Somewhat similar to Blanc, U.S. Pat. No. 5,199,422 titled Modular snorkel, issued to Stan Rasocha on Apr. 6, 1995, teaches an exhaust valve mounted on a cap that covers the upper end of the snorkel. The cap restricts the entry of splashed water into the snorkel. The exhaust valve on the cap permits the direct expulsion of water from within the snorkel during a purging exhalation. Although Rasocha's snorkel is an improvement over Blanc, it nevertheless permits water to flood the snorkel when the swimmer dives below the surface.
U.S. Pat. No. 5,960,791 titled Dry Snorkel, issued to Carl Winefordner and Frank Hermansen on Oct. 5, 1999 teaches a snorkel having an upper opening directed to the side of the snorkel tube. A diaphragm carried on the end of a short buoyant arm serves as a valve that can close the upper opening and thereby keep water from entering the snorkel. The arm pivots at its opposite end so that the diaphragm can swing toward or away from the snorkel opening. Normally, the weight of the arm moves the diaphragm away from the opening. When the arm is submerged, the arm's buoyancy will cause the diaphragm to move against the snorkel opening. As lone as the arm is underwater, the snorkel opening will be closed. A cage protectively covers the arm and diaphragm assembly. The Winefordner and Hermansen snorkel requires that respiratory flow first pass through the cage openings and then abruptly turn 90 degrees through the side opening of the snorkel. Although adequate for casual or novice swimmers, the flow restriction caused by the 90 degree turn and interference by the relatively narrow openings in the protective cage, limits performance and the snorkel is not considered satisfactory for use by experienced snorkelers.
The applicant addressed many of the problems of the prior art by the teaching of U.S. Pat. No. 6,571,108 titled Dryest Snorkel, which issued to the applicant on Apr. 16, 2002. The applicant's patent teaches a buoyant chamber, separate from the conduit, which surrounds and is coaxial with the conduit above water end. A lower opening in the chamber is joined to the conduit by a convoluted diaphragm. The convoluted diaphragm provides a flexible and watertight barrier that enables the chamber to be easily buoyed a short distance upward, guided by the snorkel conduit. The conduit's open end protrudes loosely through an upper opening in the chamber. The conduit open end carries a flexible circular diaphragm that, when it makes contact with the upper opening of the buoyed chamber, serves as a check valve allowing exhalation flow from the conduit to ambient, but blocks the flow of water into the snorkel. In addition, an optional purge valve adjacent the conduit underwater end also allows flow from the conduit to ambient, but not in the reverse direction. The check valve remains closed as lone as the chamber is underwater. When the chamber is above water, its weight causes the chamber to drop down, opening the valve. Respiratory flow moves through the annular opening between the diaphragm and the upper opening of the chamber. Although the annular opening is relatively large, some resistance to respiratory flow is introduced, making the snorkel less than perfect for use by experienced snorkelers.
In view of the foregoing factors, conditions and problems that are characteristic of the prior art, the instant invention was conceived. It is the object of the instant invention to provide a snorkel top valve that reliably prevents water from entering the open end of a submerged snorkel, but does not in any way interfere with respiratory flow when the valve is open.